A giant steel float that will be part of a "floating island" in Seoul boasting off-shore entertainment facilities began a snails-paced trip towards the city's Han River Saturday.

The football-field-sized structure, resembling the hull of a cargo ship, moved at a barely noticeable speed over rows of giant rubber airbags from a riverside assembly site to the water just 60 metres (198 feet) away.

Linked by huge iron chains to giant winches, the buoy weighing 2,000 tonnes was not due to reach the water until Sunday.

The three-metre high float, 85 metres long and 49 metres wide, will be part of Viva, one of three artificial islets to be built near the southern end of Banpo Bridge.

Along with two other artificial islets, Vista and Tera, to be launched by the end of April, the cluster of man-made floating islets will be used for conventions, water sports, restaurants, performances and exhibitions.

The project will be completed and open to the public in August.

"We hope that the floating island will serve as Seoul's new landmark," a Seoul city government spokeswoman said.